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Strained Diphosphines Built upon a Calix[4]arene Skeleton. Synthesis of a Highly Active Norbornene Polymerization Catalyst
Author(s) -
Lejeune Manuel,
Jeunesse Catherine,
Matt Dominique,
Sémeril David,
Peruch Frédéric,
Toupet Loïc,
Lutz Pierre J.
Publication year - 2006
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.200600055
Subject(s) - methylaluminoxane , norbornene , steric effects , diphosphines , catalysis , polymer chemistry , polymerization , chemistry , nickel , chelation , branching (polymer chemistry) , tetrafluoroborate , materials science , metallocene , stereochemistry , organic chemistry , polymer , ionic liquid
Summary: The complexes cis‐P , P ′‐( η 5 ‐cylopentadienyl)‐{5,17‐dibromo‐11,23‐bis(diphenylphosphino)‐25,26,27,28‐tetrapropoxy‐calix[4]arene}nickel( II ) tetrafluoroborate ( 1 ) and dibromo‐{5,17‐dibromo‐11,23‐bis(diphenylphosphino)‐25,26,27,28‐tetrapropoxycalix[4]arene}nickel( II ) ( 2 ), both of which contain a constrained chelating diphosphine, were evaluated for the polymerization of norbornene. Combined with methylaluminoxane, they result in remarkably active systems for the production of high‐molar‐mass vinyl‐type polynorbornene. Turnover frequencies of up to 7.5 × 10 5 mol(NBE) · mol(Ni) −1 · h −1 are observed. A plausible explanation for their high performances relies on a periodic P–Ni–P bite angle enlargement that temporarily increases the steric hindrance about the catalytic centre, which in turn favours the insertion steps.Molecular structure of 2 .